1. Field of the Invention
The present invention relates to a light projection apparatus, a light condensing unit, and a light emitting apparatus.
2. Description of Related Art
There are conventionally known light projection apparatus that are provided with a fluorescent member that is irradiated with laser light (see, for example, JP-A-2003-295319).
JP-A-2003-295319 mentioned above discloses a light source apparatus (light projection apparatus) provided with an ultraviolet LD element which functions as a laser light source, a phosphor (fluorescent or phosphorescent substance; fluorescent member) which converts the laser light emanating from the ultraviolet LD element into visible light, and a visible-light reflecting mirror which reflects the visible light emanating from the phosphor. In this light source apparatus, the visible-light reflecting mirror which reflects the visible light emanating from the phosphor is provided to illuminate a predetermined region ahead of the light source apparatus.
When the light source apparatus disclosed in JP-A-2003-295319 mentioned above is used, for example, as a headlamp of an automobile, the projection pattern of the light emitted from the light source apparatus needs to be controlled. Specifically, the light source apparatus needs to be designed to produce a laterally elongate light projection pattern. Although JP-A-2003-295319 mentioned above does not discuss any light projection pattern, the light projection pattern obtained is supposed to be circular. Inconveniently, this makes it difficult to use the light source apparatus disclosed in JP-A-2003-295319 mentioned above as, for example, a headlamp of an automobile, where a laterally elongate light projection pattern is required.
On the other hand, there are conventionally known light condensing members that guide laser light while condensing it (see, for example, JP-A-2007-41623). JP-A-2007-41623 discloses (paragraphs [0066]-[0069], and [0079]; FIGS. 8 to 10, and 16) an optical waveguide (light condensing member) that includes an entrance face through which laser light enters and an exit face which has a smaller area than the entrance face. In this optical waveguide, the laser light that has entered through the entrance face is guided to the exit face while being reflected on the side faces that connect between the entrance face and the exit face; the light eventually exits through the exit face in a condensed state.
Although JP-A-2007-41623 mentioned above does not discuss it, using an optical waveguide requires the use of a member that holds the optical waveguide. That is, the holding member inevitably makes contact with the surface of the optical waveguide. For example, in a case where the holding member makes contact with a side face of the optical waveguide, part of the laser light traveling inside the optical waveguide exits into, and is absorbed by, the holding member at where the optical waveguide and the holding member make contact with each other, because there the total reflection condition is not fulfilled. Inconveniently, this lowers the efficiency of use of light (laser light).
As an improvement, JP-A-2007-41623 mentioned above also discloses a structure in which an Ag layer for reflecting laser light is provided on the side faces of the optical waveguide. Since the reflectance of Ag is about 95%, however, the laser light is absorbed by the Ag layer each time it is reflected on it. This lowers the efficiency of use of light (laser light).